1. Field of the Invention
The present invention relates to an internal combustion engine and, more particularly, to an internal combustion engine of the type, in which an opening at one side of a cylinder block in the crankshaft direction is covered with a side cover.
2. Description of the Prior Art
In the internal combustion engine of the above-specified type, in which an opening is formed at one side in the crankshaft direction and covered with a side cover, one bearing of the crankshaft is disposed in that side cover. Since a lubricating oil pump is driven from the crankshaft through a cam shaft, its drive shaft is arranged in parallel with the crankshaft and is attached to the side cover or the side of a gear mechanism for driving the cam shaft. Moreover, power for driving a service machine is extracted at the side of the side cover, and the fly-wheel is attached to the opposite or outer side of the cylinder block. FIGS. 7 and 8 show the structure of a cylinder block of an internal combustion engine having a side cover structure according to the prior art.
In FIGS. 7 and 8, reference numeral 1 designates a cylinder block, and numeral 2 designates a side cover covering the opening of the cylinder block 1. To a generally middle portion of the cylinder block 1 in a direction perpendicular to the shaft, as viewed in a top plan view, there is attached a crankshaft 5 which has its one end supported in the side cover 2 through a plain bearing 3 and its other end supported in the wall of the cylinder block 1 at the side opposed to the side cover 2 by a ball bearing 4. A cam shaft 6 is arranged to one side of the crankshaft 5, and an intermediate shaft such as a balancer shaft 7 is arranged to the other side, so that the cam shaft 6 may be driven from the crankshaft 5 through a gear mechanism 8 which is attached to the crankshaft 5 and the cam shaft 6 at the side of the side cover 2. Moreover, the balancer shaft 7 is driven through a gear 9 which is attached to the crankshaft 5 and the balancer shaft 7 at the side opposed to the side cover 2. A case 10 is formed in the side cover 2 below the cam shaft 6, and a lubricating oil pump 11 which has its drive shaft 12 projecting into the cylinder block 1 is accommodated in the case 10. At the same time, a driven gear 13 fixed on the drive shaft 12 meshes with the gear mechanism 8 on the cam shaft 6 to drive the lubricating oil pump 11. To the leading end of the driven gear 13, there is attached a governor weight assembly 14 for regulating the speed. The crankshaft 5 has its end 15 projecting from the side cover 2 to provide a power extraction side, and the side cover 2 at this power extraction side is equipped at its outside with a flange 16 to be connected directly to a service machine. The (not-shown) fly-wheel is arranged at the end portion of the crankshaft 5 at the side opposed to the flange 16.
On the other hand, a speed control system of a Diesel engine is composed of a not-shown fuel injection pump, the aforementioned governor weight assembly 14, a self regulating speed mechanism for connecting the fuel injection pump and the governor weight assembly 14, and a control mechanism for adjusting the injection rate. Of these, the governor weight assembly 14 is mounted on the same shaft 12 as that of the lubricating oil pump, as described above, and is positioned at the side of the side cover 2. On the other hand, the not-shown self regulating speed mechanism and injection rate adjusting control mechanism are mounted together with the fuel injection pump in the body wall of the cylinder block 1 at the side opposed to the governor weight assembly 14 and are interlocked with the governor weight assembly 14.
In the structure of the prior art thus far described, the lubricating oil pump 11 is disposed in the side cover 2 at the power extraction side, and the driven gear 13 of the drive shaft 12 projecting from the side cover 2 into the cylinder block 1 is arranged to mesh with the gear 8 on the cam shaft 6.
Firstly, this structure has a defect in that assembly of the side cover 2 is seriously troublesome. This assembly is shown in FIG. 9. The lubricating oil pump 11 is assembled together with the drive shaft 12 and the parts on the drive shaft 12 so as to cover the opening of the cylinder block 1. At this time, it is necessary to bring the driven gear 13 on the drive shaft 12 and the gear 8 on the cam shaft 6 into meshing engagement with each other. It is rare, however, to insert the gears with their teeth completely meshing with each other. Considerable troubles are encountered in turning at least one of the gears to establish the meshing engagement by inserting the hand into a clearance 17 present before the side cover 2 is brought into abutment against the wall of the cylinder block 1.
Secondly, the lubricating oil pump 11 is attached to the side cover 2 at the power extraction side of the service machine. As a result, the flange 16 to be connected directly to some service machine will axially interfere, if disposed outside of the side cover 2, with a lubricating oil pump cover 18 which is also fixed on the outer side of the side cover 2, so that the lubricating oil pump 11 cannot be removed for inspection. As a result, the direct connection has to be given up for such service machine. In this case, it is conceivable to change the position of the flange 16 so as to avoid such interference. As a matter of fact, this change is difficult because the mounting sizes of the service machine and the flange and the direct socket connection are specified in advance.
Generally speaking, moreover, the lubricating oil discharged from the aforementioned lubricating oil pump 11 is guided from a passage formed in the wall portion of the cylinder block 1 or the side cover 2 into the bearing portion of the crankshaft 5, and is then fed to the crank pin via a bore hole formed in the crankshaft 5. In order that the lubricating oil may thus flow into the bored hole in the crankshaft 5, the bearing has to be of the plain type. Since, however, the plain bearing 3 is used only as the bearing of the side cover in the prior art, the passage from the lubricating oil pump 11 to the bearing has to be formed in the side cover 2. This passage 19 has to be obliquely machine because the lubricating oil pump 11 is disposed below the cam shaft 6 positioned obliquely above the crankshaft 5, as shown in FIG. 8. As a result, the machining is difficult, and the parting direction is complicated, even when die casting is employed, thereby causing the production costs to be high.
In addition, the driven gear 13 of the pump drive shaft 12 is in meshing engagement with the cam shaft gear 8 at the side of the side cover 2. This cam shaft gear 8 must have a large diameter because it rotates at half the speed of the crankshaft 5. As a result, the drive gear 13 must be positioned apart from the crankshaft, thus restricting the positioning of the lubricating oil pump 11. Thus, it is impossible to position the pump most efficiently.
In the prior art, moreover, the lubricating oil filter to be disposed at this side of the lubricating oil pump 11 is also disposed at the side of the side cover 2 so that it is attached and detached from the side of the service machine. Since it is difficult to integrate the case for supporting the lubricating oil filter with the side cover, it has to be formed either separately or integrally with the cylinder block 1 so that it is inserted in the vicinity of and in parallel with the side cover. The former arrangement is beset by the problem that the number of parts will increase. In the latter arrangement, the passage for introducing the lubricating oil to the bearing of the side cover 2 is cut at the joint between the side cover 2 and the cylinder block 1 so that this cut portion has to be specially sealed up. Thus, the latter arrangement also results in an increased number of parts.
In the Diesel engine, on the other hand, it is necessary to make adjustments, e.g., to set the maximum fuel injection rate at the stage in which the aforementioned speed control system is assembled. In the prior art, as described above, the governor weight assembly 14 is disposed at the side cover 2, whereas the fuel injection pump and the self regulating speed mechanism are disposed in the cylinder block 1. As a result, the speed control system is not completed until the side cover 2 is attached, thereby creating a problem in that such adjustment cannot be accomplished before the side cover 2 is attached. Thus, the adjustments have to be done under a load run in the completed state in which the cylinder block 1 is assembled and in which the cylinder head and so on are attached. This load run required after assembly involves most of the steps of the assembly process.
As described above, on the other hand, the governor weight assembly 14 and another mechanism are separately attached to the side cover 2 and the body of the cylinder block 1. As a result, their assemblies have to be separately accomplished, and the connections among the governor weight assembly 14, the self speed regulating mechanism and the adjusting control mechanism have to be accomplished at the stage in which the side cover 2 is attached. Thus, another defect is that the assemblies are troublesome and poor in accuracy.